The present invention relates to an optical recording medium for the optical recording and/or reproduction of information through physical and chemical change induced in an information recording layer of the medium, and a method for producing an optical recording medium.
The optical recording medium comprises an information recording layer containing an organic material such as a dye, a dye-polymer complex, a photosensitive polymer, a photosensitive diazo compound and a photochromic dye.
When the dye or dye-polymer complex is used as the information recording layer, it is selectively melt, vaporized or deformed by irradiation of laser light to form irregularity in the layer by which information is recorded. This way of recording is so-called heat mode recording and is based on the same mechanism as applied to a practically used chalcogen semiconductive material.
The organic photochromic dye attracts attention due to its reversibility and is studied as an erasable photone mode recording material (see for example L. M. Ralston, SPIE 420, 186 (1983)). Most of the photochromic dyes are soluble in a solvent and expected to make it possible to produce an optical recording medium such as a disc by forming its thin layer by spin coating. However, they have not been practically used.
When the photochromic dye is irradiated by light having a specific wavelength, its light absorption spectrum changes from one state to another. However, the photochromic dye in which photochromism is based on cis-trans isomerization exhibits photochromism in a solution but not in the form of a solid thin film.